Adjustable stroke pump



21, 1944.. s SCHNELL 2,344,517

ADJUSTABLE STROKE PUMP Filed June 8, 1942 2 Sheets-Sheet l INVENTORATTORNEY arch 21, 1944. s, sc-HNELL 2,344,517

ADJUSTABLE STROKE PUMP Filed June 8,- 1942 '2 Sheets-Sheet 2 5Q 45 &

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TO z S. SC LL BY Mm Patented:Mar. 2 1.1944

JUSTABLE STRQKE PM Steve Schneli, Kirkwood, Mo., assignor to Wagner-Electric Corporation tion of Delaware st. Louis, .Mo., a corpora-Application June 8. 1942, Serial No. 446,187

I 11 Claims. (Cl. 103173) My invention relates to pump'for developing.fluid pressure and more particularly to means for adjusting the strokeof the 'i'eciprocable element or elements thereof.

One of the objects of .my invention is to provide ina pump havingare'ciprocable pressure developing element, improved means for adjustingthe length ofthe stroke thereof.

, Another and more specific object of my invention is to provide strokeadjusting means in a well-'mown manner by a rotating shaft ll journaledin the housing I. The inner end of this shaft lies in compartment 3 andcarries an actuating roller i8 pivotally mounted on a pin ii of theshaft which has its axis at right angles to the axis of rotation of saidshaft. The exterior end of the shaft has secured thereto -a for thereciprocable elements of a reciprocating pump of the swash plate typehaving meansassociated therewith for controlling the conditioni-ng ofthe swash plate in order to make the pump operative or inoperative.

Other objects of my invention will become sectional view taken on theline 3-3 of Figure 2; and Figure 4 is a sectional view of.a portionmeans is embodied.

Referring first to Figure 2, there is disclosed a reciprocating pump ofthe swash plate type which is enclosed within a housing I havingcompartments 2 and 31 therein filled with a suitable liquid. A secondcasing t carries a plurality of reciprocating pumps generally indicatedby the numeral 5. These pumps may be of any number desired and areequally spaced clrcumferentially about a common axis. Each pumpcomprises a cylinder 6 having, reciprocable therein a piston I! providedwith a passage 8 for admitting fluid from compartment. 3 to thecompressing chamher 9 ahead of the piston. The piston passage iscontrolled by a check valve I0 in order that fluid may be trapped in thecompressing chamher during the forward movement of the piston.

The compressing chamber has an outlet passage 'ill' controlled by acheck valve structure l2 for preventing return flow of fluid to thecompressing vchamber after it is once forced out of said chamber. Thepistons l of the pumps have ball and-socket connections M with a swashplate I t pivotally mounted at its center by a ball and of a pump inwhich a-manual stroke adjusting pulley 20 so that the shaft can bedriven by a belt from a suitable source of power.

of the pump. Thus if this piston should be in the position shown, thepumps will not be operated by the rotation of shaft l1 since the swashplate can then'assume a position at right angles to the axis of thedriving shaftf However, if piston 16 is moved to the.right, this willmove the center of the swash plate toward the shaft and thereby cause itto be tilted, that is, lie in a plane other than a plane which is atright angles to the axis of the driving'shaft. This shaft ll, by meansof roller l8, will cause the swash plate to wobble back and forth as theroller moves around the surface of the swash plate. This causes thepistons of the pumps to be reciprocated and consequently force fluidunder pressure past the outlet valves l2.

The pumps may be employed to develop fluid pressure for use in any typeof fluid pressure actuating system. The piston I6 may be controlled invarious manners so that the pumps will be operative or inoperative asdesired. How- 'ever, by way of example, I have shown the pumpsassociated with a fluid pressure actuating' system wherein the pumps areadapted todevelop fluid pressure to actuate a brake and to be controlledby fluid pressure developed man- As shown in Figure ,1, the systemcomprises a master cylinder device 2| which has a cylinder 22 and areciprocating piston 23, said piston being operated by a piston rod 24and a pedal 25. Thepiston is normally held in its retracted position bya spring 26 which uncovers a porthole 21 for placing the cylinder incommunication with a; reservoir 28 when the piston isin its inoperativeposition.

The reservoir 20 is connected to be in constant I I communication withcompartments 2 and 3 of socket connection [5V to a movable member Itwhich is in the form of a piston. v The swash plate i4 is adapted to beactuated the pump by means ofa conduit 29 The outlet of the mastercylinder device is connected by way of conduit 30 to casing 4 tocontrol'piston I6 and a conduit 3| leads from the outlet of $118 p' gnpsto fluid motors 32 of brake assem- The movable member or piston 16 isadapted to control the operativeness and inoperativeness being largerpressure will maintain and i6 will be moved to the leftto their originalpositions. This will permit the swashplate larger than and axiallyaligned with the cylinder in which piston i6 is mounted. Within cylinder34 is a piston 36 formed as an integral extension of piston l6. Betweenthe pistons 36 and i6 is a chamber 36 which is in constant communicatlonwith the outlets of the pumps by means of passages 31. This chamber isalso in constant communication with conduit 3| leading to the fluidmotors, said communication being by way of passage 38, the end ofa'cylinder 33 (to be referred to later) and a passage 43. 'A packing cup4i seals the piston i6 and a packing cup 42 seals piston 36, said cupspreventing fluid under .pressurefrom passing the pistons from chamber36. The cup 42, however, does permit fluid to pass piston 36 in adirection so that fluid under pressure may flow from conduit 30 tochamber 36. This flow is permitted by the collapse of the cup lip and itis facilitated by passages 43 in piston 36.

The cylinder cylinder 44 by way of a passage 46, said cylinder than thepreviously mentioned cylinder 39 and forming a continuation thereof;Within cylinders 44 and 33 is a two-diameter piston 46 having a passage41 therethrough. The small end of the piston" is provided with a valveportion 48 for cooperation with a valve seat 43 so that the passage 41can be cut of! from com- 'munication with cylinder 33 and consequentlywith conduit 3| which communicates with said cylinder. A spring 66biases the valve portion 43 to a seated position. Suitable packing cups6| and 62 prevent fluid from flowing past rection. It is seen that withthe pump associated with a fluid pressure system in the mannerdescribed, when the master cylinder device is actuated to develop fluidpressure,this pressure will act upon the large piston 36 and thus forcepiston ii to the night to cause the swash plate to be actuated. therebybringing the pumps into operation'so as to develop fluid under pressure.This fluid under pressure will be forced into chamber 36 and from :4communicates with another to againassume a position wherein it will nolonger be actuated by the roller on the driving shaft il. Consequently,no more fluid pressure will be developed in the pumps. 4

when it is desired to release fluid pressure in the fluid motors, allthat need be 'done is to release the master cylinder device. There willthen be a drop in fluidpress-ure in cylinder 44, thereby resulting inthe two-diameter piston 46 being moved to the left to unseat the valveportion 46. This will open up passage 41 and fluid can then return tothe master cylinder device where it will enter reservoir 23 and pushfluid back up into compartments 2 and 3 associated with the pump.

It is desirable in a swash plate driven pump to v be able to control thestroke of the pistons so that the volume of fluid pumped can bemaintained at a desired value. When the driving shaft ll of the pump isdriven at variable speeds. the only way-this can be done is to providean automatic means for varying the stroke of the pumping pistons. Tomaintain ,a constant volume of fluid pumped, the' stroke of. the pistonsmust be decreased for an increase in shaft speed. I have accomplishedthis in the pump shown in Figure 2 by means of an adjustable meansautomatically t p riphery of the two-diameter piston in either di-'controlled by a governor.

Referring to Figures 2 and 3, a rod 63 is slidably mounted in thedriving shaft l1 and has its inner end 64 positioned adjacent thecentral part of the swash'pla'te. The other end of this rod is roundedand adapted to cooperate with cam surfaces 66 and 66 formed on pins 61and 63,

respectively, slidably carried on' -the pulley and shaft. These pins areparallel with each other and one end of pin 61 has a weight 63 securedthereto and the opposed end of pin 63 has a weight 66 secured thereto.Since these weights there out into conduit 3| and the fluid motors 32 tothus cause actuation of the brakes. The valve 43 will be held seated dueto the pressure of the fluid from the master cylinder acting upondevice. If the ratios of theseareas are taken as two to one, then thepressurein the fluid motors will always be twice that of the pressuredeveloped in the master cylinder device. In orlie on opposite sides oftheaxis of the shaft, they will move the pins outwardly and relativelyto each other under the action of centrifugal force.

A spring 6| is connected to oppose the outward movement'of the weights.

Thus with the automatic adjusting structure shown, the greater the speedof the shaft, the farther rod 63 will be moved inwardly. Since the innerend 64 of the rod lies adjacent the central part of the swash plate, itwill control the angle of tilt of the swash plate, which tilt determinesder to maintain valve 43 seated and prevent the fluid under the higherpressure from being in communication with the fluid under lowerpressure, the two-diameter piston 46 also has substantially the sameratio as the ratios of. the areas of piston 36. Thus under condiflonswhere flfty pounds per square inch of fluid pressure is developed by themaster cylinder device, this piston IS in such a tion that the pumpswill continue to be operated until they develop one hundred pounds persquare inch of pressure. When this occurs, pistons 36 the stroke of thepistons, and thus it is seen'that the stroke of each piston can bevaried. If we assume, for example, that the Weights 63 and 63 will notmove outwardly when the speed of the shaft is under four hundredrevolutions per minute then the stroke of thepumps'wili be a maximum forspeeds under this flgure, this stroke being determined by the distancebetween the end of rod 64 and the central surface of the swash platewhen the swash plate is in its vertical position as shown in Figure 2.With a shaft speed of four hundred revolutions per "minutethe pumps willpump a certain volume offluid. As the speed of the driving shaftincreases, the

' weights 63 and 63 will move outwardly, thus moving rod 63 inwardly.This inward movement of rod 63 will push the center of the swash plateto the left, consequently decreasing the stroke of the pistons. Withshorter strokes at higher shaft speed the volume of fluid pumped willremain approximately the same as it was with the longer stroke and thelower shaft speed.

Thus it is seen that when the pump i driven by a source of power whichhas a variable speed, the pump, nevertheless, can be caused to pumpsubstantially constant volumes for a unit of time.

If the pump shaft should be driven by a power means having a constantspeed, it, of course, will not be necessary to have any automatic meansfor adjusting the stroke of the pump pistons. However, there should bemanual adjusting means provided so that the volume of fluid being pumpedfor a given speed can be changed. The manual adjusting means shown inFigure 4 can be employed to accomplish stroke adjustments. Referring nowto this figure, the pumping structure is the same as previouslydescribed. However, in place of rod 53 there is substituted a rod 3'which has a threaded end 62 cooperating with threads 63 in the end ofshaft H. A screwdriver receiving slot 64 is provided in the outer end ofthe rod for turning the rod and thus move it axially with respect toshaft i1 so as to vary the amount of tilt of the swash plate. The outerend of the rod has cooperating therewith a threadednut 65 which actsboth as a protecting means and a locking nut to hold the rod in adjustedposition.

With this. manual adjusting means it is seen that if the driving shaftis being rotated at a constant speed, as, for example, six hundredrevolutions per minute, the swash plate can be adjusted so that thestroke of the pumps will pump.

a given volume of fiuidper interval of time. If the driving shaft shouldhave a speed of only four hundred revolutions per minute and the samevolume is desired to be pumped, then an adjustment can be made so as tocause the pumps to have a longer stroke.

Being aware of the possibility of modifications in the particularstructure herein described without departing'from the .iundamentalprinciples of my invention, I do not intend that its scope be limitedexcept as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. In a pump of the swash plate type, a pin-- rality o1 reciprocablecircumferentially spaced pistons, a swash plate pivotally mounted at itscenter and connected to the pistons adjacent its periphery, a rotatabledriving member for the swash plate, means for moving the pivot of theswash plate from a position where the swash plate is not actuated by itsdriving member to an actuated position, a stop for limiting the movementof the swash plate, and means for adjusting the position of the stop.

2. Ina pump of the swash plate type, a plurality of reciprocablecircumferentially spaced pistons, a swash plate pivotally mounted at itscenter and connected to the pistons adjacentits periphery, a rotatabledriving member for the swash plate, means for moving the pivot of.the

swash plate from a position where the swash plate is not actuated by itsdriving member to an actuated position, a stop for limiting the movementof the swash plate, and means for auto-- matically adjusting theposition of the stop in accordance with the speed of, the rotatabledriving member.

3. In a pump of the swash plate type, a plu rality of reciprocablecircumferentially spaced pistons, a swash plate pivotally mounted at itscenter and connected to the pistons adjacent its periphery, a rotatabledriving member for the swash plate, means for moving the pivot of theswash plate from a. position where the swash plate is not actuated byits driving member to an actuated position, a stop for limiting the movement of the swash plate, and means for automatically adjusting theposition of the stop in ac- 5 cordance with the speed of the rotatabledriving member, said last named means comprising move able weightsmounted on the driving member and movable by the action of centrifugalforce.

4-.In a pump of the swash plate type, aplurality *of reciprocablecircumferentially spaced pistons, a swash plate pivotally mounted at itscenter and connected to the pistons adjacent its periphery, a rotatabledriving member for the swash plate, means for moving the pivot of theswash plate from a position where the swash plate is not actuated by itsdriving member to an actuated position, a-member carried by the drivingmember and positioned to be engaged by the central'part of the swashplate and'provide a stop therefor when moved to the actuated position,

and means for'adjusting the position of the stop member. I I

5. In a pump, a plurality of parallel cylinders arranged about a centralaxis, pistons in the cyl-; inders, means for reciprocating the pistonsincluding a rotatable driving member and a swash plate having a pistonactuating position in which it is tilted with respect to a plane normalto the axis of the rotatable driving member, and means 0 responsive tothe speed of the driving member for varying the angle of tilt.

6. In a pump, a plurality of parallel cylinders arranged about a centralaxis, pistons in the 'cylinders, means for reciprocating the pistonsincluding a rotatable driving member and a swash plate having a pistonactuating position in which it is tilted with respect to a plane normalto the axis of the rotatable driving member, a stop for limiting theangle of tilt, means for moving the swash plate to the tilted positionas determined by the stop, and means for adjusting the position of thestop to ther'by vary the angle of tilt.

' 7. In a pump, a plurality of parallel cylinders arranged about acentral axis, pistons in the cylinders, a swash plate pivotally mountedat the central axis and connected to actuate the pistons, a drivingshaft having a part rotatable in a fixed circular path and so engageablewith the swash plate as to cause the swash plate to be wobblederate withthe swash plate at its pivot for adjusting the relative axial positionsof the pivot of the swash plate and the swash plate engaging part on theshaft to thereby vary the stroke of the pistons. 8. In a pump, aplurality of parallel cylinders arranged about a central axis, pistonsin the cylinders, a swash plate pivotally mounted at the central axisand connected to actuate the pistons, a driving shaft having a partrotatable in a fixed circular path and so engageable with the swashplate as to cause the swash plate to be wobbled and sequentiallyreciprocate the pistons, and.

means for adjusting the relative axial positions of engaging part on theshaft to thereby vary the stroke of the pistons, said adjusting meanscomprising a rod carried by the shaft having an end engaging with theswash plate at its pivot for moving its pivot and means for moving saidrod;

9. In a pump, a plurality of cylinders and pi tons grouped abouta'central axis and adapted to [develop fluid under pressure, a swashplate pivoted at its center and. connected to the piston at radiallyspaced points, arotatable driving memthe pivot of the swash plateand theswash plate her for actuating the swash plate, fluid pressure operatedmeans for moving the pivot of the swash plate to a position where it canbe engaged and wobbled by the driving member to operate the pistons, andadjustable stop means associated with the swash plate for varying theposition the pivot or the swash plate is caused to assume by the fluidpressure operated means.

10. In a pump, a plurality of parallel cylinders arranged about acentral axis, pistons in the cyl-- inders, a swash plate for actuatingthe pistons, means for pivotally mounting the swash plate on the centralaxis, 'a rotatable element having a fixed circular path of movement fordirectly cooperating with the peripheral portion of the swash plateradially outward of its pivot, and means carried solely by the rotatableelement and cooperating with the swash plate at its pivot for ad- Ilusting the position of the pivot 01 the swash and means carried solelyby the rotatable element vthe operative angle of the swashs'ravnscnnmh'.

and responsive to the speed of the rotatable element for-adjusting theposition the movable member and pivot of the swash plate may assume withrespect to the rotatable element to thereby vary stroke of the pistons.

to the rotatable element to plate and the

